With newborn hearing screening now identifying children with hearing loss in infancy, a better understanding is needed about specific child, family, and service factors that lead to optimal development of these infants as they mature. Relatively little is known about the variables that facilitate optimal social-emotional and adaptive functioning for these young children in real-world environments. The objectives and design of our proposed study take transactional/ecological theoretic approach of child development, which purports that development in young children is influenced by many interrelated factors, including biological, social, and cultural. Based on this theoretical framework, we propose that the developmental trajectories for young children with mild to severe hearing loss are best understood within a complex context that includes child variables, family/parent characteristics, and intervention services available to the child and family. The specific aims of this project are: 1) to determine the developmental trajectories of young children with mild to severe hearing loss with respect to social-emotional and adaptive functioning and to compare these developmental patterns to those of young children with typical hearing;2) to examine the relations between language skills and social-emotional and adaptive development in young children with mild to severe hearing loss;and, 3) to examine the influence of parenting and intervention factors on language development and social-emotional and adaptive functioning in young children with mild to severe hearing loss. To accomplish these aims, we propose a longitudinal multicenter study of 210 children diagnosed with mild to severe sensorineural hearing loss, and a group of 100 typical hearing children for comparison purposes. The children will be followed from 12 to 48 months of age and assessed under the outcome domains of audition, speech perception, language, cognition, social- emotional problems and competencies, and adaptive functioning. Parents will be assessed in terms of their involvement and self-efficacy, emotional availability, and language input. Lastly, specifics of intervention services are considered to be important variables and will be delineated throughout the investigation. Multi-Level Modeling will be implemented as part of the analytic plan, permitting descriptions of trajectories for social-emotional and adaptive functioning, as well as testing specific hypotheses regarding associations with related child, family, and intervention service characteristics. This project brings together developmental perspectives from multiple disciplines, including audiology, speech-language pathology, developmental and clinical psychology, early intervention, pediatrics, otolaryngology, and biostatistics. The knowledge gained from this longitudinal investigation will inform developmental theory and should promote effective and responsive child and parent support interventions for young children with mild-to-severe hearing loss.